¹IIT Bombay, Powai, Mumbai-400 076, India

Total Ref : 62

Optimization of Efficiency in a 1D Grating Structure at 1310nm Wavelength for Application in Optical Interconnect

G Palai¹, *S K Tripathy², N Muduli³, S K Patnaik²

¹Gandhi Institute for Technological Advancement, Bhubaneswar

²National Institute of Science and Technology, Berharmpur

³Gandhi Engineering College, Bhubaneswar

This paper optimizes the diffraction efficiency of 1D silicon-a silicon grating structure at wavelength 1310 nm. Optimization is made with respect to absorption and transmission losses using plane wave expansion (PWE) method. The simulation results showed the efficiency of 1D grating structure is more than 99% for 1 µm-1 µm, 1 µm-4 µm, 4 µm-1 µm and 10 µm-1 µm thickness of silicon-a silicon layer at 1310 nm. 

Keywords: 1 D grating, PWE, Reflectance, SOI

Total Ref : 12

Fluctuations induced conductivity in YBYBa₂Cu₃O_7-d  + x oFe₂O₄ composites

M Sahoo^a, B Bhol^a, D Behera^a,*

Fluctuations on the electrical conductivity of polycrystalline YBa₂Cu₃O_7-d  + x CoFe₂O₄(x = 0.0, 0.1, 0.2, and 0.3 wt.%) superconductors were investigated from the resistivity vs. temperature(R-T) data. Attempts have been made to identify the optimum inclusion of ferromagnetic CoFe2O4 particles in YBa₂Cu₃O_7-d δ (YBCO) superconductor. With the increase of CoFe₂O₄ addition, it is found that the superconducting transition temperatures (Tc) determined from standard four-probe method and magnetization vs. temperature (M-T) studies, were decreased and dropped sharply with higher wt.% addition of CoFe₂O₄. M-T graphs shows that the composites satisfy Meissner effect. Excess conductivity fluctuation analysis using Aslamazov-Larkin (AL) model fitting reveals transition of two dominant regions (2D and 3D) above Tc. The decrease in 2D-3D crossover temperature (TLD) (Lawerence-Doniach temperature) in the mean field region has been observed as a consequent dominance of 3D region with increase in wt.% of CoFe₂O₄ in the composite.

Total Ref : 18

Dynamic study of phonon excitation spectrum in some heavy fermion systems

J Sahoo^1*, N Shadangi² and P Nayak³

¹Regional office of vocational Education, Sambalpur

²Padmashree Krutartha Acharya College of Engineering, Bargarh

The phonon excitation spectrum of some Heavy Fermion (HF) systems in the presence of electron-phonon interaction is studied in the dynamic limit (ω¹i H*0). The renormalized excitation phonon frequencies (ώ=ω/ω0) are evaluated through Periodic Anderson Model (PAM) in presence of electron –Phonon interaction using Zubarev type double time temperature dependent Green function .The calculated renormalized phonon energy is analyzed through the plots of (ώ=ω/ω0) against temperature for different system parameters like effective coupling strength ‘g’, the position of f-level‘d’ and the onsite coulomb interaction ‘U’. The observed behaviour is analyzed and found to agree with the general features of HF systems found in experiments

Total Ref : 18    

Dielectric anomaly in Na₂Pb₂Dy₂W₂Ti₄Nb₄O₃₀ ceramic

L Biswal^1,3, Piyush R Das^2,*, and Banarji Behera³

¹Department of Physics, SOT, KIIT University, Bhubaneswar – 751 024, Odisha, India

²Department of Physics, ITER, S. O. A. University, Odisha, Bhubaneswar – 751 030, India

A new polycrystalline ceramic Na₂Pb₂Dy₂W₂Ti₄Nb₄O₃₀ was prepared by high temperature solid state reaction technique. Preliminary X-ray diffraction (XRD) study showed the formation of single-phase compound in an orthorhombic structure. Surface morphology of the compound was studied by scanning electron microscopy (SEM). The frequency and temperature dependence of dielectric properties (er and tand) of the compound was investigated in the frequency range of 102 to 106 Hz and temperature range 300K to 800 K. The ceramic compound showed non-relaxor type diffused dielectric anomaly at 577K. Ferroelectric property of the compound was confirmed with polarization (hysteresis) study. Using modified Curie-Weiss law around transition temperature, the order and type of transition has been suggested.

Keywords: Ceramics; Sintering; Dielectric Properties; Hysteresis

Total Ref : 24

Analysis of grains grown on pond-ash treated soils

K C Patra^a,b, N R Mahapatra^c,d, P  Nayak^a, and Tapash R. Rautray^d,e*

^aDepartment. of Physics, Sambalpur University, Jyoti Vihar, Sambalpur – 768 019, Odisha, India

^bInstitute of Physics, Sachivalaya Marg, Bhubaneswar – 751005, Odisha, India

^cDepartment of Physics, Silicon Institute of Technology, Patia, Bhubaneswar, Odisha, India

^dCentre of Excellence in Theoretical and Math Sciences, SOA University, Bhubaneswar – 751030, Odisha, India

Elements namely Mn, Fe, Cu, Zn, Mo and Pb were determined in the current study by using Energy dispersive X-ray fluorescence (EDXRF) technique. The increase in yield of the rice grains using pond ash was 16% and 22% produced at Malud and Dhenkanal (in Orissa, India) respectively as compared to their control values. The concentration of trace elements in rice grains was well below the critical levels in the plants for human consumption.

Total Ref : 17

Competence of 4H-SiC IMPATT diode for terahertz application

J Pradhan¹, S K  Swain¹, G N Dash¹ and S R Pattanaik²

¹School of Physics, Sambalpur University, Jyoti Vihar, Sambalpur-768 019, Odisha, India

The competence of 4H-SiC material for being used as a base material for possible terahertz application was examined following our computer simulation method. The computed power density value of 8.3 × 1011 W/m2 with a DC-to-RF conversion efficiency of 11% at the operating frequency of 1.0 THz are note worthy. A significant negative conductance value of 9.7×108 Sm–2 and a noise measure of 56dB are also computed at the frequency of 1.0 THz using a small signal model for sub-mm-wave or terahertz applications. The results speak about the potential of SiC material for terahertz application.

Keywords: Terahertz, IMPATT, 4H-SiC

Total Ref : 20

Synthesis and characterization of Na₂Pb₂Y₂W₂Ti₄Ta₄O₃₀ ferroelectric ceramic

S Behera¹, Piyush R Das^2*, P Nayak³ and R N P Choudhary²

²Department of Physics, Hi-tech College Engineering, Bhubaneswar- 751 025, India

²Department of Physics, Institute of Technical Education & Research, Siksha OAnusandhan
University, Bhubaneswar-751015, Odisha, India 

In the present work, sample of composition Na₂Pb₂Y₂W₂Ti₄Ta₄O₃₀ (NYT) was prepared by a high-temperature solid-state reaction technique. X-ray diffraction (XRD) analysis reveals the formation of single-phase compound with an orthorhombic structure at room temperature. Surface morphology of the compound was studied by scanning electron microscope (SEM). Temperature dependence of dielectric constant indicates the presence of two dielectric anomalies at 408K and 586K, which may be attributed to the ferroelastic-ferroelectric and ferroelectric-paraelectric transitions respectively as suggested by hysteresis loop at room temperature. Complex impedance spectroscopy analysis has been carried out as a function of frequency at different temperatures to establish the correlation between microstructure and electrical properties of the material. The frequency dependence of ac conductivity obeys the Jonscher’s universal power law. The values and nature of temperature variation of dc conductivity exhibit the NTCR behavior of the material like a semiconductor.

Keywords: Electronic material; Ferroelectricity; XRD; Electrical conductivity.

Total Ref : 34 

Study of interface sheet charge density of AlGaAs/InGaAs/GaAs-based pseudomorphic HEMT

T R Lenka, Sudhakar Das, Rasmita Ku Nayak, G N Dash and A K Panda

In this paper a new AlGaAs/InGaAs/GaAs based pseudomorphic heterostructure device is proposed and various subbands are calculated by solving 1D Schrodinger and Poisson’s equation self-consistently in the heterostructure by applying suitable boundary conditions. The interface sheet charge density (ns) for each subband is calculated from the various eigenvalues by numerical approach. The conduction band profile followed by the formation of 2DEG and electric field as a function of distance (Ao) are also discussed. The 2DEG density and electric field at the heterointerface are measured to be 1.092 ´ 1012 cm–2 and 2 ´ 105 V/cm respectively. The dependency of interface charge density on doping density of barrier layer and thickness of spacer is also discussed.

Index Terms: 2DEG, HEMT, Heterostructure, MBE, Pseudomorphic, Subband

Total Ref : 9

Impedance-Spectroscopy Analysis of (Bi_0.5Na_0.5)TiO₃ –SrTiO₃ Lead-Free  Ceramic Systems

B Parija^1,2 & S Panigrahi^1*

¹Department of Physics, NIT, Rourkela-769008, India

The polycrystalline (1-x)(Bi_0.5Na_0.5)TiO₃ –xSrTiO₃ (x = 0.01, 0.05 & 0.09) (abbreviated as BNT-ST) ceramics have been synthesized by conventional solid state sintering technique. X-ray diffraction analysis indicated that a solid solution is formed when SrTiO₃ diffuses into the (Bi_0.5Na_0.5)TiO₃ lattice and revealing that the system is stable perovskite type structure. The microstructure indicated that the grain size reduces and the shape changes from rectangular to quasispherical with increasing in SrTiO₃ content. Complex Impedance Spectroscopy analysis suggested the presence of temperature-dependent relaxation process in the materials. The ac conductivity was found to obey the universal power law. The activation energies have been calculated from the dc conductivity(increases with increasing of ST content) which suggests that the conductions are ionic in nature.  

Keywords: Impedance Spectroscopy; Electrical Modulus; Relaxations; Conductivity

Total Ref : 28 

^bDepartment of Physics, ITER, Bhubaneswar

Lanthanum-doped strontium vanadates, Sr₅LaTi₃V₇O₃₀, were prepared by a high-temperature sold-state reaction method. The formation of the materials was checked by X-ray diffraction technique. Preliminary structural analyses of the materials exhibit the formation of single-phase orthorhombic structures. Surface morphology of the compounds was studied by scanning electron microscopy. The effect of La on microstructure of the materials has resulted in a modification of the electrical properties. Study of electrical properties using impedance analysis technique exhibit;
(i) the presence of negative temperature coefficients of resistance behavior, (ii) presence of temperature dependent electrical relaxation phenomena, (iii) evidences of single electrical relaxation attributed to the presence of bulk contribution to the electrical properties, (iv) an enhancement in the barrier to the mobility of charge carriers on La-substitution.

Keywards: X-ray diffraction; Phase transitions; Dielectric loss and relaxation

PACS: 77.22.Ch; 77.22.Ej; 77.22.Gm; 77.80.Bh

Total Ref : 9 

 Structural and electrical properties of Sr modified Rare earth doped ceramics

BB Mohanty, P S Sahoo, R N P Choudhary

aDepartment of Physics, Betnoti College, Betnoti, Mayurbhanj, Orissa, India

The polycrystalline sample of Sr₅GdTi₃V₇O₃₀, a member of tungsten bronze structural family, was prepared by a high-temperature solid-state reaction technique. A preliminary X-ray diffraction analysis suggests the formation of single-phase compound with orthorhombic structure. The effect of temperature (32- 400°C) and frequency (102–106 Hz) on electrical properties were studied using an impedance analyzer. A typical negative temperature coefficient of resistance (NTCR) behavior has been observed in this material.

Keywards: X-ray diffraction; SEM; Electrical conductivity

PACS: 77.22.Ch; 77.22.Ej; 77.22.Gm; 77.80.Bh

Total Ref : 15

Institute of Materials Science, Planetarium Building, Bhubaneswar-751013, India

Total Ref : 17

Swati Mishra, S K Tripathy and Mihir Hota

Coupling of power in fiber optics communication is one of the important and challenging tasks. Several conventional methods for coupling are in uses which have their own merits and demerits. Recently coupling of power using Holographic technique is proposed. We in this paper investigated the design of an effective Coupler based on Hologram diffraction efficiency. It is found that, by increasing the refractive index modulation the thickness of the coupler can be decreased without affecting the diffraction efficiency. The design procedure for such a Holographic grating is also explained.

Keywards: Holograting, Diffraction efficiency, Recording geometry, Reconstruction geometry

 Vol. 21, No 2 (2012)225-232

Complex impedance study of NaSr₂Nb₅O₁₅ ceramic

S K Satpathy¹, N K Mohanty¹, Banarji Behera¹, P Nayak¹ and R N P Choudhary²

¹Materials Research Laboratory, School of Physics, Sambalpur University,
Jyoti Vihar, Burla – 768 019, Odisha, India

²Department of Physics, ITER, Siksha ‘O’ Anusandhan University, Bhubaneswar – 751 030, India

Total Ref : 19

 Vol. 21, No 2 (2012)233-240

Studies of structural and dielectric properties of layered bismuth oxide: BaBi₂V₂O₉

N K Mohanty, R N Pradhan, B Behera and P Nayak

Material Research Laboratory, School of Physics, Sambalpur University, Jyoti Vihar,Burla-768 019, Odisha, India 

Total Ref : 16 

A Pattanaik^1* and P Nayak¹

Transition metal dichalcogenides 2H-MX₂ (M=Nb, Ta, X= S, Se) are materials with layered structure. These structures show large anisotropy in electrical, optical, magnetic and transport properties. Particularly, NbS2 shows large anisotropy not undergoing a charge density transition but is extreme type-II superconductor for lower applied field remaining in the mixed state. In view of this, in lower applied field limit, the order parameter is assumed to be spatially constant and the vortex cores are treated as singularities. Using the anisotropic formulation of the London limit for the two applied field directions, we have tried to explain the temperature dependence of change in specific heat. The anisotropic ratio g has also been calculated in terms of in plane and out plane penetration depths and found a qualitative agreement with the experimental findings.

Total Ref : 20

N Shadangi¹, J Sahoo² and P Nayak³

¹Padmashree Krutartha Acharya College of Engineering, Bargarh,Odisha

²Regional office of vocational Education, Sambalpur768001, Odisha

³School of Physics, Sambalpur University,Jyoti Vihar, Burla-768019,Sambalpur, Odisha